Process and apparatus for the production of magnesium by electrolysis



March 20, 1934. v QBIEDOFF 1,951,836

PROCESS AND APPARATUS FOR THE PRODUCTION OF MAGNESIUM BY ELECTROLYSISFiled Feb. 15, 1932 Patented Mar. 20, 1934 UNITED STATES PATENT OFFICErnocsss AND APPARATUS ron run PRO- DUCTIGN 0F TROLYSIS MAGNESIUM BYELEG- Vladimir Obiedoif, Paris, France, assignor to Soclete de ProduitsChimiquea des Terrcs Bares,

Paris, France Application February 15, 1932, Serial No. 593,188

Germany February 19, 1931 9 Claims.

- such that the metal is enabled to collect in a compact homogeneousliquid mass, and when the magnesium is allowed to accumulate for severalhours instead of being removed from the vat as fast as it is formed.This lengthy accumulation aids the collecting of the metal into globulesand also the elimination of impurities due to the bath, such as thechlorides forming the electrolyte itself and the traces of oxides andother solid materials carried in suspension in the electrolyte, whichcanthus be separated from the metal.

For this purpose, when proceeding according to the invention, a suitablespace or chamberis formed in which the magnesium will collect, thischamber being given the greatest possible depth which will not undulyraise the voltage of the vat, by means of a relatively deep immersion ofthe vertical partitions which form the sides of the said chamber inwhich the magnesium collects, and in the lower extremity of which thecathode is situated. The chamber thus formed serves for the accumulationof a rather large quantity of magnesium, this, quantity having arelatively considerable thickness, for instance 10 centimeters, and thedepth to which the said partitions may descend is limited only as statedabove, by the electrical design of the vat. The metal will thus collectin the chamber so provided, sufliciently removed from the chlorine to beprotected from its action, and free from all disturbances whiclymay takeplace in the anode chamber, and the metal may remain polarized in thischamber, if desired. The magnesium may be removed for instance twice aday, as this gives the metal a sufliclent time to collect and for theimpurities tosettle out.

The invention has further for its object a particular method for theremoval of the magnesium which is formed, due to the fact that theapparatus now contains a certain quantity .of-

magnesium in the form of a thick layer. According to this method, themagnesium is drawn oil by a conduit or tube, leading from the mass ofmagnesium.

For this purpose, the electrolytic vat comprises a discharge conduitprovided with means for closing the same, controlled from the exterior,said conduit being located in a region which is sufficiently hot toprevent all obstruction by solidiflcation of the magnesium in theconduit. This method of removal by direct outflow has the advantage ofaffording a marked saving of labor.

The following description, together with the accompanying drawing, givenby way of example, shows a particular embodiment of the invention.

Figure 1 is a vertical section along the line 1-1 of Figure 2, of anelectrolytic vat according to the invention.

Figure 2 is a corresponding section along the line II-II of Figure 1.

It is to be observed that in the said vat, thepartitions which (in planview) bound the space in which the magnesium accumulates, descend intothe bath to a considerable depth, and thus the magnesium accumulates inthe form of a layer 2 of relatively great thickness, for instance 10centimeters. The cathode 3 issituated at the bottom of the vat, andhence the partitions 1 can be lowered to the proper point withoutreducing the efliciency of the apparatus, as the region of electrolysisis thus maintained at the lower part of the bath. I

The magnesium deposited on the cathode collects in small sphericalparticles which slide upwards along the sides of the cathode and collectin a compact mass in the cathodic space or chamber.

This accumulation in a thick layer also permits drawing of! of the metalby direct outflow, siphon discharge or the like, by means of a suitablyplaced conduit, which has hitherto been found impracticable, the metalbeing removed from the vat in the hitherto known processes as soon aspossible after its formation, and thus only existing in the vat in thestate of separate globules, or at the most, in a thin continuous layerwhich cannot be drawn oil? by a fixed conduit without bringing with it aconsiderable portion of the electrolyte. Q In the construction hererepresented, the metal is evacuated by gravity by means of a tubeconduit leading from the mass of metal and so arranged that thetemperature therein shall be sumcient to avoid all serious obstructionowing to solidification of the metal.-

. In the example shown the conduit 4 is a metallic conduit which isplaced against the cathode and-ends at 5 in the upper portion of theaccumulated layer of magnesium. As it is in contact with the cathode,the said conduit has the same polarity as the latter, and it may furtherparticipate in the cooling oi. the cathode if this In the particularcase shown in Figure 2, the discharge conduit or tube extends along thecathode 3 for its whole lower length, and until it emerges out of thevat, and thus, as the said conduit has the same polarity as the cathode,it is certain that the metal deposited on the conduit will collect withthe rest of the metal in the cathodic space or chamber.

In this form of construction, the said conduit is stopped at the outletof the furnace by a plug 6 of refractory material. The plug might besituated at the other end of the conduit, means being provided forcontrolling it from the exterior.

Obviously, instead of a single tube 5, it is feasible to employ aplurality of such tubes, suitably distributed in the cathodic chamber.Or again the discharge might be so arranged as to take place at theupper level of the mass of magnesium, in which case it would not benecessary to employ a special tube.

The intake 5 of the said conduit should be situated as high as possiblein the layer 2 of magnesium, as in the first place the impurities aregreater in amount in the lower portion of the layer, and in the secondplace, when the metal is run oif, owing to the hydrostatic effectproduced by the flow of the electrolyte around the partitions the upperlevel 0-4) will vary but little, while the lower level rises from c-d toc'd'.

I claim:

1. Process for the production of magnesium by the electrolysis ofmagnesium chloride, which consists in maintaining the resultingmagnesium free from all agitation, and in allowing it to accumulate in arefractory walled chamber which constitutes no part of the electriccircuit, in the form of a homogeneous mass having a substantial depth,whereby the impurities in the magnesium will be separated from'thislatter.

2. Process for the production of magnesium by the electrolysis ofchloride, which consists in maintaining the resulting magnesium freefrom all agitation, and in allowing it to accumulate in a refractorywalled chamber which constitutes no part of the electric circuit, in theform of a homogeneous mass constituting the product of at least severalhours, whereby the impurities in the magnesium will be separated fromthis latter.

3. Electrolytic vat for the electrolysis of molten MgCla, said vatcontaining a cathode and an anode, and a cathodic chamber whereinmagnesium liberated at the cathode can accumulate, said cathodic chamberbeing made of refractory material and forming no part of the electriccircult of said cell, the entire cathode being posi-' tioned within theplan of the interior of such chamber and below the bottom thereof, saidchamber being bounded by partitions of refractory material extendingdown into the electrolyte to a depth suflicient to ensure that-the metalis able to accumulate in a layer of sufficient thick ness to permit ofthe depodtion of impurities.

4. Electrolytic vat according to claim 3, characterlzed by the fact thatthe cathode is situated in the lower portion of the vat, in such amanner that the top of the cathode is situated at a lower levelthan thebottom of the partitions forming the cathodic chamber, all ofhe cathodearea being beneath the plan of said cathodic chamber.

5. Electrolytic vat according to claim 3, in which the partitionsbounding said cathodic chamberextenddownintothebathtoasomewhat greaterdepth than said anode, whereby the gas given off at the anode is allgiven off at a height above the bottom of said cathodic chamber, and ata higher level than the zone of communication of the part of the bath inthe anodic magnesium chamber and the part of the bath in the cathodicchamber.

6. Improvement in processes for the production of magnesium according toclaim 1, characterized by the fact that the magnesium formed by theelectrolysis is drawn off from. the cell in a liquid state by means of aconduit having its upper orifice in the homogeneous layer of moltenmagnesium, and near the upper level of this molten layer.

7. In the production of metallic magnesium, the herein described stepswhich comprises maintaining a bath of molten magnesium chloride in anelectrolytic cell, maintaining inter-communicating portions in suchbath, which communicate with each other only below the level of thebottom of an inner compartment of said cell, all of the cathode surfacebeing positioned below the interior of said compartment, the anodesbeing positioned outside said compartment and wholly away from thebottom thereof, whereby gases liberated at said anodes cannot flowtoward the bottom of said compartment nor toward the zones ofcommunication between the anode compartment and said inner compartment,allowing a considerable depth of metallic magnesium to accumulate insaid inner compartment, and allowing sufllcient time of quiescentstorage of said in said irmer compartment for particles of magnesiumchloride to settle out of the upper portion of said body of moltenmagnesium, and finally withdrawing molten magnesium from well above thebottom of. said body of metallicmagnesium.

8. In an apparatus for the electrolysis of magnesium chloride, anelectrolytic cell having anodes which enter the same at the top, acathode entering the bottom of the cell from below, an interiorcompartment defined by walls of refractory material, closed at the top,and open at the bottom, covering the entire cathode surface in the cell,such interior compartment being of considerable depth, to allow themolten magnesium to rise into said interior compartment, said interiorcompartment communicating with the compartment containing the anode onlyat its bottom, whereby the molten material in said interior compartmentis not materially agitated by gas evolved at the anode, and entry of anyof such gas into said interior compartment is prevented.

9. In an apparatus for the electrolysis of magnesium chloride, anelectrolytic cell having anodes which enter thesame at the top, acathode entering the bottom of the cell from below, an

interior compartment defined by walls of refractory material, saidinterior compartment bein closed at the top and open at the bottom andcovering the entire cathode surface in the cell and being of suillcientsize to hold all of the metallic magnesium which the cell can produce-,during a period of at least several hours, said inby gas evolved at theanode, and entry of any of such gas into said interior compartment isprevented.

VLADIMIR QBIEDOFI".

